The present invention relates to materials used in fabricating temporary access mats and matting systems and, more particularly, presents a unique formulation of synethetic materials for use in constructing matting for use as temporary roads and work surface areas.
Wooden mats have tradionally been utilized in the oil and gas and construction industries to form temporary roads and access areas at drill site locations and other construction sites. The temporary roads and access areas are formed by laying individual wooden mats in a desired pattern. This pattern of individual mats provide access over and around work areas with poor soil conditions that would otherwise be inaccessible to heavy trucks and construction equipment. When the drilling or construction is completed these mats can be removed for utilization elsewhere.
The use of wooden mats present certain disadvantages. The mats are typically made of layers of wood timbers spiked or bolted together. The timbers forming the mats are subject of splitting, warping, breakage and disposal in compliance with state and federal regulations. Mats having split, broken or warped surfaces can produce imperfections in the matted surfaces that impede the access of the heavy equipment or cause damage to the equipment. The wooden mats used to form the matted surfaces are also expensive, require substantial maintenance, and increase the demand on forests that produce timber and timber products. Wooden mats are also heavy and can be difficult to move, place and store.
Applicants"" herein propose a temporary construction mat for use in matting systems formed from a unique combination of synthetic structural materials. U.S. Pat. No. 5,653,551 to Seaux suggests a mat system having individual mats comprised of composite materials. Seaux proposes a combination of virgin resins, plastics, reclaimed polyolefins and vulcanized rubber in further combination with strengthening agents such as fiberglass, steel, graphite, nylon or combinations of the materials. However, the Seaux patent makes no suggestion as to a preferred proportion or combination of such composite materials to be used in forming the mat.
There are problems associated with the use of synthetic materials to form construction matting. Construction matting is subjected to heavy vehicle loads more often than not in areas of poor soil conditions. Mats must be sufficiently rigid to distribute the vehicle loading over the matted area. Mats composed of synthetic materials, when subjected to loading, often have a pronounced deflection due to the characteristics of the materials from which the mat is formed. Such mats often retain too much xe2x80x9cmemoryxe2x80x9d from this deflection creating a permanent deformation in the matting. This retained memory or deformation impedes the mats ability to distribute the traffic loads to the soil surface. Further, the use of synthetic materials in matting may create enhanced electrostatic properties causing sparking with an increased risk of explosion. Mats constructed from structural members made with certain synthetic materials may also present problems due to separation of component parts of the mat when conventional fasteners such as screws, spikes or bolts are used to secure the mat components together. The Seaux patent does not present a formulation of synthetic materials to address these problems.
Others have suggested the use of synthentic materials, particularly waste plastics and elastomers, for making construction materials. Examples of such are described in U.S. Pat. No. 5,030,662 to Banerjie and in U.S. Pat. No. 5,759,680 to Brooks. Both the Banerjie and Brooks patents primarily feature the use of various polyethylenes as the bulk of the matrix forming structural member. The Banerjie patent teaches the use of polyolefins in conjunction with compatibilizers, impact modifiers and reinforcing agents in the matrix forming the structural member. The Brooks patent teaches the use of polyolefins in conjunction with cellulosic fibers in the matrix of the structural member. Neither presents a formulation of synthetic materials to address the aforementioned problems presented when such materials are used in construction matting.
Scrap rubber has also been suggested for use as a componet in the formulation of synthetic building materials. In U.S. Pat. No. 5,439,735 to Jamison rubber is suggested as a component material for particle board products, because of its resistance to decay, water, rot, insects, and its thermal and acoustic properties.
In U.S. Pat. No. 4,244,841 to Frankland a method of using grindings of scrap tire rubber is proposed for producing structures such as paving stones, floor coverings, resilient bumpers for highway guardrails, and railroad tie pads. In U.S. Pat. No. 4,851,500 to Lalwani teaches a process for blending scrap as a component of the material used in making roofing, walkway pads, and tiles. U.S. Pat. No. 5,886,078 to Sullivan et al. discloses the use of polymeric composites comprising thermoplastic polyolefins, a rubbery polymeric component, and reinforcing filler as a replacement for wood.
None of the aforementioned disclose the unique combination of rubber and synthetic components having the structural and physical properties of flexibility without retaining load memory and low electrostatic characteristics. They were found by applicants to be required for temporary matting to be used in the oil and gas construction industries.
The present invention presents a unique formulation for synthetic structural material blended and extruded primarily from high density polyethylene (HDPE), polyethylene terephthalate (PET), and styrenexcx9cbutadiene rubber (SBR). The unique formulations presented herein, when appropriately specified, offer building materials that are long lived, flexible, without retaining load xe2x80x9cmemoryxe2x80x9d and that are resistant to ultraviolet light, ozone, weather, insect and microbial degradation and electrostatic buildup. A further desired characteristic of the structural materials blended and extruded as described and claimed herein, is a material having a desired low electrostatic potential.
The formulations described and claimed herein also impart qualities to the structural members so produced that facilitate their use as construction material as they accommodate the use of traditional tools and traditional fasteners such as spikes, nails, screws and bolts. In addition, the formulations described and claimed result in producing structural materials having excellent compressive, shear and tensile strength, and high moduli of elasticity and rupture as determined by ASTM standard test methods.
While the precise amounts of each of the components above may vary according to the desired properties of the ultimate matrix, and while particle sizes and particle preparation may affect the characteristics of the final product material, it is thought that the formulations instructed herein, within the general range, and percentages of materials described, will achieve the specific listed and desired material characteristics for use as construction matting.
The primary components of HDPE, PET, and SBR can be obtained from virgin materials manufacturers and/or distributors. In addition to component availability through new material suppliers, these components are widely available through recovered materials markets. The reutilization of these polymers is widely recognized to be of paramount importance to conserve energy, landfill space, and other resources given that such materials represent a considerable percentage of the overall waste stream and volumes are generally increasing every year. Although many modern composite materials that specify SBR prefer to utilize xe2x80x9cdevulcanizedxe2x80x9d feed stocks owing to their much improved cross-linking/bonding abilities, for most of the applications addressed herein, simple, physical preparations and detail to particle size needs, result in products achieving the desired characteristics.